The supported highly active and highly stereospecific catalysts for the polymerization of propylene and higher olefins known up to now are obtained by the reaction of an Al alkyl compound partially complexed with an electron-donor compound (outside donor) with a solid component comprising a Ti compound and an electron-donor compound (inside donor) supported on a Mg dihalide in active form.
Examples of such catalysts have been described in British Patent No. 1,559,194 and Belgian Patent No. 868,682.
Outside donors consisting of silicon compounds containing Si--O--C bonds have been described, also, in published Japanese patent applications Sho 79/94590 and Sho 80/36203.
Among the various and numerous inside donors such compounds as methylmethacrylate and ethyl pivalate have been cited.
However, in all the prior art catalysts in which a silicon compound containing Si--O--C bonds is used as outside donor, esters of benzoic acid and derivatives thereof are used as inside donor.
The performance of the above catalysts, expressed in terms of activity and stereospecificity, is not different from the performance of the catalysts in which ethyl benzoate and similar esters of benzoic acid are used as outside donor.